BookingWP - WooCommerce Appointments 4.21.6

* Improvement - Compatibility with WordPress 6.4.
* Improvement - Include quantity field as hidden even when customer cannot choose the qty.
* Improvement - Removed excessive caching that could cause query issues.
* Improvement - gCal additonal staff ID checks when syncing.
* Improvement - Updated all translations.
* Fix - Free products status stays in-cart instead of paid.
* Fix - Big issue when booking multiple appointments in one order with 100% discount.
* Fix - Addons add a + sign even if the value is negative - fix it.
* Fix - Skip staff ID's on sync attempt when empty.
* Fix - Cannot assign appointments to existing orders with COT enabled.
* Fix - WooCommerce TM Extra Product Options not working, when product quantity is missing.

* Improvement - Compatibility check with WooCommerce TM Extra Product Options 6.3.2.
* Improvement - Compatibility with WooCommerce 8.2.
* Improvement - Updated Product Add-ons to 6.5.0.
* Improvement - Better integration with Product Add-ons blocks.
* Improvement - Updated all translations. Added lots on new strings.
* Fix - Additional checks to make sure only appointments are rendered in templates.

* Improvement - Compatibility with WordPress 6.3.
* Fix - Some addons missing closing DIV element - breaks layout of the site.
* Fix - gCal for staff not working.